How atrial fibrillation may affect your brain

Bouts of atrial fibrillation, or afib — a rapid, chaotic heartbeat — make some people feel lightheaded and dizzy, while others don’t notice any symptoms. But the most serious threat of this condition is the higher risk of stroke among people with afib compared with those without the disorder (see “Blood clot dangers, large and small”). Now, there’s a growing recognition that people with afib also face an increased risk of thinking and memory problems — even if they do not experience a stroke.

Known as cognitive impairment, these problems include trouble remembering, learning new things, concentrating, or making routine decisions. The presumed underlying cause? Tiny blood clots that cause “silent” (that is, unrecognized) strokes and gradually injure parts of the brain involved with cognition.

“Until recently, very little was known about the association between afib and cognitive impairment,” says Dr. Moussa Mansour, director of the atrial fibrillation program at Harvard-affiliated Massachusetts General Hospital. But an expert consensus statement on arrhythmias and cognitive function, published March 23 in the Journal of Arrhythmia, outlines the evidence for the connection and offers advice for preventing the problem.

Blood clot dangers, large and smallIllustration by Scott LeightonDuring atrial fibrillation, the upper chambers of the heart (atria) quiver rapidly instead of contracting forcefully. This causes blood to pool inside the left atrium, where it stagnates and may form clots. If a clot escapes the atrium, it can travel to (and block) a blood vessel in the brain. Large clots can cause a stroke, which may affect your ability to move, speak, or even swallow. The effects of tiny clots often go unnoticed. But over time, these so-called silent strokes may accumulate and cause thinking and memory problems.

Minor but cumulative damage

Silent strokes usually don’t cause noticeable symptoms because they are very small and often occur in the front of the brain rather than in areas that affect movement and speech, Dr. Mansour explains. “But in people with afib, these tiny strokes tend to recur over the years, and the damage is cumulative.” Brain imaging studies suggest that afib doubles the risk of silent strokes. These, in turn, are linked to a higher risk of cognitive decline.

Drugs that help prevent blood clots (also called anticoagulants or blood thinners) are a vital part of afib treatment. All anticoagulants increase the risk of potentially dangerous bleeding in the gastrointestinal tract or brain, which is why they aren’t appropriate unless a person’s stroke risk outweighs the risk of bleeding. To decide, doctors use a tool that considers other stroke risk factors, such as age, sex, and cardiovascular problems (see “A scoring system for people with afib”).

A scoring system for people with afib

Add up your points to see if you should be taking an anticoagulant.

Age 64 to 74

+1

Age 75 or older

+2

Female

+1

High blood pressure

+1

Diabetes

+1

Heart attack or peripheral artery disease

+1

Stroke, transient ischemic attack (TIA), or a clot elsewhere in the body

+2

Heart failure

+1

TOTAL

0 = no treatment recommended1 = aspirin, warfarin, or a NOAC*2 and higher = warfarin or a NOAC*

*Novel oral anticoagulant. These include apixaban (Eliquis), dabigatran (Pradaxa), edoxaban(Savaysa), and rivaroxaban (Xarelto) and may be preferred over warfarin.

The benefits of clot prevention

For decades, warfarin (Coumadin) was the drug of choice for stroke prevention. But it requires frequent monitoring and possible dose adjustments, and it interacts with many foods and other drugs. Now, doctors are more likely to prescribe novel oral anticoagulants (NOACs), which don’t have the same downsides. Compared with warfarin, NOACs are at least as effective for preventing strokes and are less likely to cause dangerous bleeding in the brain, says Dr. Mansour. However, an estimated 40% of people with atrial fibrillation who should be taking an anticoagulant drug are not, he says. According to the consensus statement, people with afib who qualify for anticoagulation therapy should consider taking a NOAC, which may also help prevent cognitive impairment by preventing strokes.

People with afib should also focus on other healthy habits to lower their risk. These include exercising, losing weight if you’re overweight, and treating sleep apnea, high blood pressure, and high cholesterol. Many studies show an association between alcohol consumption and afib, so Dr. Mansour suggests limiting alcohol to occasional use if you have afib.

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